Thermotropic liquid crystalline polymers are classified as “rigid rod” polymers as their molecular structure is typically composed of aromatic units linked by functional groups such as esters and/or amides. The rigid, rod-like structure allows the polymers to exhibit liquid crystalline behavior in their molten state (thermotropic nematic state). High molecular weight liquid crystalline polymers have interesting properties, such as a high melt viscosity, high thermal stability, and enhanced flow along with good mechanical properties. These properties make them attractive in diverse fields such as sheet extrusion, thermoforming processes, etc. For these types of applications, it is advantageous to have a material with high melt strength or enhanced “low shear” viscosity. Due to the high melting points of these polymers (e.g., above about 350° C.), however, the melt viscosity required for these applications is very high and must be obtained by solid-state polymerization. In a solid-state polymerization process, a low molecular weight, melt polymerized prepolymer is heated below its melting point (and above its glass transition temperature) so that chain-extension can take place and result in a higher molecular weight resulting in increased melt viscosity of the polymer. However this process can be quite time-consuming and thus can significantly add more cost to the product.
As such, a need currently exists for a technique of accelerating the build-up of viscosity during solid-state polymerization, which can in turn decrease the time needed to achieve the required melt viscosity.